The present invention relates to the field of immunology and is particularly concerned with outer membrane proteins from Moraxella, methods of production thereof, genes encoding such proteins and uses thereof.
Otitis media is the most common illness of early childhood with approximately 70% of all children suffering at least one bout of otitis media before the age of seven. Chronic otitis media can lead to hearing, speech and cognitive impairment in children. It is caused by bacterial infection with Streptococcus pneumoniae (approximately 50%), non-typable Haemophilus influenzae (approximately 30%) and Moraxella (Branhamella) catarrhalis (approximately 20%). In the United States alone, treatment of otitis media costs between one and two billion dollars per year for antibiotics and surgical procedures, such as tonsillectomies, adenoidectomies and insertion of tympanostomy tubes. Because otitis media occurs at a time in life when language skills are developing at a rapid pace, developmental disabilities specifically related to learning and auditory perception have been documented in youngsters with frequent otitis media.
M. catarrhalis mainly colonizes the respiratory tract and is predominantly a mucosal pathogen. Studies using cultures of middle ear fluid obtained by tympanocentesis have shown that M. catarrhalis causes approximately 20% of cases of otitis media (ref. 1xe2x80x94Throughout this application, various references are referred to in parenthesis to more fully describe the state of the art to which this invention pertains. Full bibliographic information for each citation is found at the end of the specification, immediately preceding the claims. The disclosures of these references are hereby incorporated by reference into the present disclosure).
The incidence of otitis media caused by M. catarrhalis is increasing. As ways of preventing otitis media caused by pneumococcus and nontypeable H. influenzae are developed, the relative importance of M. catarrhalis as a cause of otitis media can be expected to further increase.
M. catarrhalis is also an important cause of lower respiratory tract infections in adults, particularly in the setting of chronic bronchitis and emphysema (refs. 2, 3, 4, 5, 6, 7, and 8). M. catarrhalis also causes sinusitis in children and adults (refs. 9, 10. 11, 12, and 13) and occasionally causes invasive disease (refs. 14, 15, 16, 17, 18, and 19).
Like other Gram-negative bacteria, the outer membrane of M. catarrhalis consists of phospholipids, lipopolysaccharide (LPS), and outer membrane proteins (OMPs). Eight of the M. catarrhalis OMPs have been identified as major components. These are designated by letters A through H, beginning with OMP A which has a molecular mass of 98 kDa to OMP H which has a molecular mass of 21 kDa (ref. 20).
Recently, a high-molecular-weight outer membrane protein of M. catarrhalis was purified and characterized (ref. 21). The apparent molecular mass of this protein varies from 350 kDa to 720 kDa as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). This protein appears to be an oligomer of much smaller proteins or subunits thereof of molecular mass 120 to 140 kDa and is antigenically conserved among strains of Moraxella.
A similar protein named UspA was also reported to be present on the surface of this species of bacteria with an apparent molecular mass of 300 to 400 kDa (ref. 22). Judging from the molecular mass, these two proteins may be the same.
M. catarrhalis infection may lead to serious disease. It would be advantageous to provide other outer membrane proteins for M. catarrhalis and genes encoding such proteins for use as antigens in immunogenic preparations including vaccines, carriers for other antigens and immunogens and the generation of diagnostic reagents.
The present invention is directed towards the provision of purified and isolated major outer membrane protein of Moraxella catarrhalis and other Moraxella strains, having an apparent molecular mass of about 200 kDa.
In accordance with one aspect of the invention, there is provided an isolated and purified, outer membrane protein of a Moraxella strain having a molecular weight of about 200 kDa, as determined by SDS-PAGE, or a fragment or an analog thereof. The outer membrane protein may be substantially in its native conformation (so as to have substantially retained the characteristic immunogenicity of the outer membrane protein in the Moraxella strain) and may be isolated from a M. catarrhalis strain, such as from M. catarrhalis 4223. Such isolated and purified about 200 kDa outer membrane protein is substantially free from non-200 kDa outer membrane protein, phospholipids and lipopolysaccharide of Moraxella. The about 200 kDa outer membrane protein is at least about 70 wt % pure, preferably at least about 90 wt % pure, and may be in the form of an aqueous solution thereof.
The present invention also provides a purified and isolated nucleic acid molecule encoding an outer membrane protein of a strain of Moraxella having a molecular mass of about 200 kDa, as determined by SDS-PAGE, or a fragment or an analog of the outer membrane protein. The protein encoded by the nucleic acid molecule may encode a protein containing the amino acid sequence NH2-Asn-Val-Lys-Ser-Val-Ile-Asn-Lys-Glu-Gln-Val-Asn-Asp-Ala-Asn-Lys-x-Gln-Gly-Ile (SEQ ID No: 2) for Moraxella catarrhalis strain 4223 or containing the corresponding amino acid sequence from other Moraxella strains.
In a further aspect of the present invention, there is provided a purified and isolated nucleic acid molecule having a sequence selected from the group consisting of (a) the sequence set out in FIG. 6 (SEQ ID No: 1), or the complementary sequence thereto; (b) a sequence encoding an about 200 kDa protein of a strain of Moraxella and containing the amino acid sequence NH2-Asn-Val-Lys-Ser-Val-Ile-Asn-Lys-Glu-Gln-Val-Asn-Asp-Ala-Asn-Lys-x-Gln-Gly-Ile (SEQ ID No: 2), or the complementary sequence thereto; and (c) a nucleotide sequence which hybridizes under stringent conditions to any one of the sequences defined in (a) or (b). The nucleic acid preferably defined in (c) has at least about 90% sequence identity with any one of the sequences defined in (a) or (b).
The nucleic acid molecules provided herein may be included in a vector adapted for transformation of a host. The nucleic acid molecules provided herein also may be included in an expression vector adapted for transformation of a host along with expression means operatively coupled to the nucleic acid molecule for expression by the host of the about 200 kDa outer membrane protein of a strain of Moraxella or the fragment or the analog of the outer membrane protein. A transformed host containing the expression vector is included within the invention, along with a recombinant outer membrane protein or fragment or analog thereof producible by the transformed host.
The expression means may include a nucleic acid portion encoding a leader sequence for secretion from the host of the outer membrane protein or the fragment or the analog of the outer membrane protein. The expression means may include a nucleic acid portion encoding a lipidation signal for expression from the host of a lipidated form of the outer membrane protein or the fragment or analog thereof.
The present invention further includes a live vector for delivery of the outer membrane protein of the invention or a fragment or analog thereof, comprising a vector containing the nucleic acid molecule provided herein. The live vector may be selected from the group consisting of E. coli, Salmonella, BCG, adenovirus, poxvirus, vaccinia and poliovirus.
In accordance with a further aspect of the present invention, there is provided a peptide having no less than six amino acids and no more than 150 amino acids and containing an amino acid sequence corresponding to a portion only of the outer membrane protein of the invention, or a fragment or analog thereof. The peptide may be one having the amino acid sequence NH2-Asn-Val-Lys-Ser-Val-Ile-Asn-Lys-Glu-Gln-Val-Asn-Asp-Ala-Asn-Lys-x-Gln-Gly-Ile (SEQ ID No: 2) for the Moraxella catarrhalis 4283 strain or the amino acid sequence for the corresponding peptide for other strains of Moraxella.
The present invention also provides an immunogenic composition comprising an immunoeffective amount of an active component, which may be the outer membrane protein or fragment or analog thereof, nucleic acid molecules, recombinant outer membrane proteins, fragments or analogs thereof, live vectors, and/or peptides as provided herein, along with a pharmaceutically acceptable carrier therefor with the active component producing an immune response when administered to a host, which may be a primate, particularly a human. The immunogenic composition may be formulated as a vaccine for in vivo administration to a host to confer protection against diseases caused by a bacterial pathogen that produces the about 200 kDa outer membrane protein or produces a protein capable of inducing antibodies in the host specifically reactive with the about 200 kDa outer membrane protein. In particular, the bacterial pathogen is a strain of Moraxella, particularly M. catarrhalis. The immunogenic composition may be formulated as a microparticle capsule, ISCOM or liposome preparation. The immunogenic composition may be used in combination with a targeting molecule for delivery to specific cells of the immune system as to mucosal surfaces. The immunogenic compositions of the invention (including vaccines) may further comprise at least one other immunogenic or immunostimulating material and the immunostimulating material may be at least one adjuvant. Suitable adjuvants for use in the present invention include, (but are not limited to) aluminum phosphate, aluminum hydroxide, QS21, Quil A, calcium phosphate, calcium hydroxide, zinc hydroxide, a glycolipid analog, and octadecyl ester of an amino acid, a muramyl dipeptide and a lipoprotein. Advantageous combinations of adjuvants are described in copending U.S. patent application Ser. No. 261,194 filed Jun. 16, 1994, assigned to the assignee hereof and the disclosure of which is incorporated herein by reference. The invention further includes an antibody specific for the outer membrane protein provided herein producible by immunizing a host with an immunogenic composition provided herein.
In a further aspect of the invention, there is provided a method of generating an immune response in a host comprising administering thereto an immuno-effective amount of the immunogenic composition as provided herein. The immune response may be a humoral or a cell-mediated immune response. The immune response may provide protection to the host against diseases caused by a bacterial pathogen that produces the about 200 kDa outer membrane protein or produces a protein capable of inducing antibodies in the host specifically reactive with the about 200 kDa outer membrane protein. Hosts in which protection against disease may be conferred include primates including humans.
The present invention provides, in an additional aspect thereof, a method of producing a vaccine comprising administering the immunogenic composition provided herein to a test host to determine an amount and a frequency of administration of the active component to confer protection against disease caused by a bacterial pathogen that produces the about 200 kDa outer membrane protein or produces a protein capable of inducing antibodies in the host specifically reactive with the about 200 kDa outer membrane protein, and formulating the active component in a form suitable for administration to a treated host in accordance with said determined amount and frequency of administration. The treated host may be a human.
A further aspect of the present invention provides a method of determining the presence of nucleic acid encoding an outer membrane protein of a strain of Moraxella having a molecular mass of about 200 kDa, as determined by SDS-PAGE, in a sample, comprising the steps of:
(a) contacting the sample with the nucleic acid molecule provided herein to produce duplexes comprising the nucleic acid molecules and any said nucleic acid molecule encoding the outer membrane protein present in the sample and specifically hybridizable therewith; and
(b) determining the production of the duplexes.
In yet a further aspect of the invention, there is provided a method of determining the presence of antibodies specifically reactive with outer membrane protein of a strain of Moraxella having a molecular mass of about 200 kDa, in a sample, comprising the steps of:
(a) contacting the sample with the outer membrane protein as provided herein to produce complexes comprising the outer membrane protein and any said antibodies present in the sample-specifically reactive therewith; and
(b) determining production of the complexes.
In a further aspect of the invention, there is also provided a method of determining the presence of an outer membrane protein if a strain of Moraxella having a molecular mass of about 200 kDa, in a sample comprising the steps of:
(a) immunizing a subject with the immunogenic composition as provided herein, to produce antibodies specific for the outer membrane protein;
(b) contacting the sample with the antibodies to produce complexes comprising any outer membrane protein present in the sample and said outer membrane protein specific antibodies; and
(c) determining production of the complexes.
The outer membrane protein may be part of a Moraxella catarrhalis strain.
The present invention provides, in a yet further aspect, a diagnostic kit for determining the presence of nucleic acid encoding an outer membrane protein of a strain of Moraxella having a molecular mass of about 200 kDa, as determined by SDS-PAGE, in a sample, comprising:
(a) the nucleic acid molecule as provided herein;
(b) means for contacting the nucleic acid with the sample to produce duplexes comprising the nucleic acid molecule and any said nucleic acid present in the sample and hybridizable with the nucleic acid molecule; and
(c) means for determining production of the duplexes.
In yet a further aspect of the invention, there is provided a diagnostic kit for determining the presence of antibodies in a sample specifically reactive with the outer membrane protein of a strain of Moraxella having a molecular mass of about 200 kDa, as determined by SDS-PAGE, comprising:
(a) the outer membrane protein as provided herein;
(b) means for contacting the outer membrane protein with the sample to produce complexes comprising the outer membrane protein and any said antibodies present in the sample; and
(c) means for determining production of the complexes.
The invention also provides a diagnostic kit for detecting the presence of an outer membrane protein of a strain of Moraxella having a molecular mass of about 200 kDa, in a sample, comprising:
(a) an antibody specific for the about 200 kDa outer membrane protein as provided herein;
(b) means for contacting the antibody with the sample to produce a complex comprising the outer membrane protein and outer membrane-specific antibody; and
(c) means for determining production of the complex.
In a further aspect of the invention, there is provided a method of producing an isolated and purified outer membrane protein of a strain of Moraxella having a molecular mass of about 200 kDa, is determined by SDS-PAGE, comprising the steps of:
(a) providing a cell mass of the Moraxella strain;
(b) disrupting the cell mass to provide a cell lysate;
(c) fractionating the cell lysate to provide a fraction containing the outer membrane protein substantially free from other cell lysate components, and
(d) recovering said outer membrane protein.
The bacterial strain may be Moraxella catarrhalis. The cell lysate may be fractionated by gel electrophoresis.
In this application, the term xe2x80x9cabout 200 kDa proteinxe2x80x9d is used to define a family of outer membrane proteins of M. catarrhalis having molecular mass of between about 160 and 230 kDa and includes proteins having variations in their amino acid sequences including those naturally occurring in various strains of Moraxella. The purified and isolated DNA molecules comprising a gene having an open reading frame of the about 200 kDa protein of the present invention also include those encoding functional analogs of the about 200 kDa protein. In this application, a first protein or peptide is a xe2x80x9cfunctional analogxe2x80x9d of a second protein if the first protein is immunologically related to and/or has the same function as the second protein or peptide. The functional analog may be, for example, a fragment of the protein or a substitution, addition or deletion mutant thereof.
Advantages of the present invention include:
a method for isolating purified about 200 kDa outer membrane protein of a Moraxella strain that produces the outer membrane protein, including Moraxella catarrhalis; 
an isolated and purified about 200 kDa outer membrane protein isolatable from a Moraxella strain; and
diagnostic kits and immunological reagents for specific identification of Moraxella and hosts infected thereby.